The disclosure relates generally to blades, and more particularly, to a cooling circuit feed duct, a cooling circuit exhaust duct, and a related cooling structure.
Blades are used in turbine applications to direct hot gas flows and generate power from the gas flows. For example, in steam and gas turbine applications, stationary blades are referred to as nozzles, and are mounted to an exterior structure such as a casing and/or an internal seal structure by endwalls. Each endwall couples to an end of the airfoil of the blade.
In order to operate in extreme temperature settings, the airfoil and endwalls need to be cooled. For example, in some settings, a cooling fluid is pulled from a cooling fluid source in the form of the wheel space and directed to internal end walls for cooling. In contrast, in many gas turbine applications, later stage nozzles may be fed cooling fluid, e.g., air, extracted from a source such as a compressor. Outer diameter endwalls receive the cooling fluid directly, while inner diameter endwalls receive the cooling fluid after it is routed through the airfoil from the outer diameter. For example, this routing may be performed by passing the cooling fluid through an impingement insert (also known as a baffle) within a core passage of the airfoil and into a pressurized diaphragm that is separate from and positioned radially internal from the endwall. Once the cooling fluid is in the diaphragm, the cooling fluid is directed radially outward to a cooling circuit in the endwall. The endwall cooling circuit can take a variety of forms such as a pin-pedestal arrangement, an impingement arrangement and/or serpentine passage in the endwall that directs the cooling fluid to necessary portions of the cores thereof. One challenge relative to cooling circuits is ensuring the cooling fluid flow reaches all regions of the cooling circuit, e.g., corners of the circuit, and does not stagnate with inactive velocity.